The present invention relates to a method for determining the ignition control variables for an internal combustion engine with occurring acceleration.
A method for determining ignition control variables is described in xe2x80x9cBosch Technische Unterrichtung, Kombiniertes Zxc3xcnd-und Benzineinspritzsystem mit Lambda-Regelung, Motronicxe2x80x9d (Bosch Technical Instruction, Combined Ignition And Fuel Injection System With Lambda Control, Motronic) (1987722011, KH/VDT-09.895-DE).
In this known ignition control unit, the various operating parameters such as rpm, load, pressure, temperature are detected via appropriate sensors at the periphery of the internal combustion engine and the relayed to the control unit. The detected sensor signals are processed in assigned sensor signal processing circuits and units, respectively, it being possible for such processing circuits to be arranged both outside the control unit and within the control unit itself. An arithmetic processor of the control unit then determines the corresponding ignition control variable based on, among other things, the signals available, preferably based on the rpm signal and load signal. For this determination an ignition map is stored in the control unit which spans rpm and load. The engine characteristics maps have been, for example, determined previously on an engine test bench in the application corresponding to optimum operating conditions. A knock control is assigned to this determination of the ignition control variable, the knock control retarding the ignition point from the knock limit after a combustion knock in that cylinder. Moreover, an additive adjustment of the ignition point obtained from the engine characteristics map is assigned to the determination of ignition point, the additive adjustment shifting the previously determined ignition point as a function of the occurring dynamics. By calculating in a dynamic derivative action, the ignition point is retarded. Subsequently, this additive adjustment is regulated over time and the ignition point is again changed in the direction of the engine characteristics map ignition point. The additive change ensures that the ignition point is not too close to the knock limit, thereby avoiding combustion knock. Finally, under acceleration, the adjustment of the ignition point results in a maximum torque being supplied. With extreme acceleration which would result in an abrupt change in the ignition point and consequently a deterioration of performance, this change is implemented slowly and only in cases in which a rapid change is absolutely necessary, for example, in the transition from part load to full load, does the control unit allow a rapid, abrupt change.
In contrast to the known methods, the method according to the present invention has the advantage that by introducing a second dynamic threshold, from which an adaptation of the dynamic derivative action to advanced takes place, the operation of the internal combustion engine takes into account the requirements that a low dynamic threshold for the output of the derivative action and a high dynamic threshold for the adaptation to advanced are established. This results in an improved interaction between the adaptation and the output of the dynamic derivative action and consequently its effectiveness.
It is particularly advantageous to determine the two dynamic thresholds in the application and to store them in a memory. An additional advantage results from storing the dynamic derivative action to be output when the first dynamic threshold is exceeded in an engine characteristics map which spans load and rpm. In this way, the change of the ignition point can be adapted very effectively to the instantaneous operating state. Finally, an additional advantage results from the stepwise return of the adaptation of the dynamic derivative action to advanced since this results in smoother vehicle performance and consequently greater ride comfort.